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The present invention relates to aerosol dispensing devices, and in particular to valve assemblies that provide automatic dispensing of aerosol content at predetermined time intervals, without requiring the use of electrical power.
Aerosol cans dispense a variety of ingredients. Typically, an active is mixed with a propellant which inside the can is at least partially in a gas state, but may also be at least partially dissolved into a liquid containing active. Typical propellants are a propane/butane mix or carbon dioxide. The mixture is stored under pressure in the aerosol can. The active mixture is then sprayed by pushing down/sideways on an activator button at the top of the can that controls a release valve. For purposes of this application, the term xe2x80x9cactive chemicalxe2x80x9d is used to mean that portion of the content of the container (regardless of whether in emulsion state, single phase, or multiple phase), which is in liquid phase in the container (regardless of phase outside the container) and has a desired active such as an insect control agent (repellent or insecticide or growth regulator), fragrance, sanitizer, and/or deodorizer alone and/or mixed in a solvent, and/or mixed with a portion of the propellant.
Pressure on a valve control button is typically supplied by finger pressure. However, for fragrances, deodorizers, insecticides, and certain other actives which are sprayed directly into the air, it is sometimes desirable to periodically refresh the concentration of active in the air. While this can be done manually, there are situations where this is inconvenient. For example, when an insect repellant is being sprayed to protect a room overnight (instead of using a burnable mosquito coil), the consumer will not want to wake up in the middle of the night just to manually spray more repellant.
There a number of prior art systems for automatically distributing actives into the air at intermittent times. Most of these rely in some way on electrical power to activate or control the dispensing. Where electric power is required, the cost of the dispenser can be unnecessarily increased. Moreover, for some applications power requirements are so high that battery power is impractical. Where that is the case, the device can only be used where linkage to conventional power sources is possible.
Other systems discharge active intermittently and automatically from an aerosol can, without using electrical power. For example, U.S. Pat. No. 4,077,542 relies on a biased diaphragm to control bursts of aerosol gas at periodic intervals. See also U.S. Pat. Nos. 3,477,613 and 3,658,209. However, biased diaphragm systems have suffered from reliability problems (e.g. clogging, leakage, uneven delivery). Moreover, they sometimes do not securely attach to the aerosol can.
Moreover, the cost of some prior intermittent spray control systems makes it impractical to provide them as single use/throw away products. For some applications, consumers may prefer a completely disposable product.
However, many dispensing devices permit liquid with active to pass through a variety of narrow control passages in the valve. Over time, this can lead to clogging of the valve, and thus inconsistent operation. In U.S. Pat. No. 4,396,152 an aerosol dispensing system was proposed which separately accessed the vapor and liquid phases of the material in the container. However, this device did not achieve reliable automatic operation.
Thus, a need still exists for improved, inexpensive automated aerosol dispensers that do not require electrical power.
In one aspect the invention provides a valve assembly that is suitable to dispense an active chemical from an aerosol container where the container has a first region holding a gas propellant and a second region holding an active chemical. The assembly is of the type that can automatically iterate between an accumulation phase where the gas is received from the container, and a spray phase where the active chemical is automatically dispensed at intervals. The regions need not be physically separated from each other. In fact, the preferred form is that the first region be an upper region of the can where propellant gas has collected above a liquid phase of the remainder of the can contents.
There is a housing mountable on an aerosol container. A movable diaphragm is associated with the housing and linked to a seal, the diaphragm being biased towards a first configuration. An accumulation chamber is inside the housing for providing variable pressure against the diaphragm. A first passageway in the housing is suitable for linking the first region of the aerosol container with the accumulation chamber, and a second passageway links the second region with an outlet of the valve assembly.
When the diaphragm is in the first configuration the seal can restrict the flow of active chemical out the valve assembly. When the pressure of chemical inside the accumulation chamber exceeds a specified threshold, the diaphragm can move to a second configuration where the active chemical is permitted to spray from the valve assembly.
In preferred forms a porous material is disposed within the first passageway to regulate the flow rate of gas propellant there through. The diaphragm shifts back to the first configuration from the second configuration when pressure of the gas propellant in the accumulation chamber falls below a threshold amount.
The accumulation chamber will exhaust the gas when the diaphragm is in the second configuration. The gas propellant and active chemical may mix in the valve assembly outside of the can. Alternatively and preferably, the active chemical and gas propellant may exit the dispenser as separate streams.
There may also be a container that is linked to the valve assembly, and an actuator portion of the housing that rotates to allow gas propellant to leave the container and enter the first passageway. The seal may be displaceable in an axial direction to allow gas propellant to flow through the first passageway into the accumulation chamber.
Methods for using these valve assemblies with aerosol containers are also disclosed.
The present invention achieves a secure mounting of a valve assembly on an aerosol can, yet provides an actuator that has two modes. In one mode the valve assembly is operationally disconnected from the actuator valve of the aerosol container (a mode suitable for shipment or long-term storage). Another mode operationally links the valve assembly to the aerosol container interior, and begins the cycle of periodic and automatic dispensing of chemical there from. Importantly, periodic operation is achieved without requiring the use of electrical power to motivate or control the valve.
The valve assembly has few parts, and is inexpensive to manufacture and assemble. Moreover the separate accessing of the gas propellant lets the gas (as distinguished from more viscous liquid) motivate the diaphragm and thus provides for cleaner and more reliable operation. By not requiring liquid and vapor to both pass through the porous media, there is much less likelihood for clogging due to extended use over months. Using the separation concepts described in this patent, product is released under full pressure with liquid propellant (as in a typical manually operated aerosol can), so as to provide for very effective particle break-up. If in a device like the present one the propellant gas was not separated from the main product, it might separate in the accumulation chamber or elsewhere in the device, thereby providing inconsistent results.